Mechanical and electrochemical properties of Nb2O5, Nb2O5:Cu and graphene layers deposited on titanium alloy (Ti6Al4V)

• Nb2O5 thin film improves titanium alloy surface hardness from 5.64 GPa to 8.64 GPa.
• icorr for graphene monolayer deposited on Ti6Al4V surface decreases to 0.01 μA/cm2.
• Ecorr for graphene monolayer deposited on Ti6Al4V surface decreases to 0.011 V.
• Graphene monolayer caused decrease in the electrochemical activity of the Ti surface.

In this paper the comparative studies on structural, mechanical and corrosion properties of Nb2O5/Ti, Nb2O5:Cu/Ti–Al–V and graphene/Ti alloy systems have been investigated. The pure nioba and nioba with copper addition were deposited on Ti6Al4V titanium alloy surface by magnetron sputtering method. Graphene monolayer was transferred on titanium alloy substrate using “PMMA-mediated” method. The structural characteristics of obtained thin films were examined by using of Raman spectroscopy, SEM and AFM measurement. The mechanical properties i.e.: nanohardness, were performed by using nanoindenter. Corrosion properties of the coatings were determined by analysis of the voltammetric curves.The deposited Nb2O5 and Nb2O5:Cu coatings were crack free and exhibited good adherence to the substrate, no discontinuities of the thin films were observed and the surface morphology was homogeneous. Graphene transferred on titanium alloy surface was a single layer without defects.The hardness of pure niobium pentoxide was ca. 8.64 GPa, nioba with copper addition was equal 7.79 GPa and graphene depositied on titanium alloy surface was equal 5.63 GPa. As obtained results show, graphene monolayer has no effect on surface hardness of titanium alloy. However, sample Ti6Al4V coated with a single layer of graphene is characterized by the best corrosion resistance. Similar results were obtained for the sample covered by 210 nm thick Nb2O5:Cu thin film.It seems, that the combined advantages of these three layers, i.e., niobium pentoxide, niobium with copper addition and a monolayer of graphene, in the hybrid multilayer system can greatly improve the mechanical and corrosion properties of the titanium alloy surface. This hybrid system can be used in the future, as protection coatings for Ti alloy, in biomedical application and in other application, where Ti alloy works in an aggressive corrosive environment and in engineering applications where friction is involved.